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Description : Check out this medical presentation on Ophthalmological Surgery, which is titled "REFRACTIVE SURGERIES", to know about refractive surgeries.

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Published on : Jul 20, 2021 | Views : 1942 | Downloads : 5

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Slide 1-

REFRACTIVE SURGERIES Dr.Jyoti Shetty Medical Director, Bangalore West Lions Superspeciality Eye Hospital
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CLASSIFICATION -R.K. -PRK -LASIK -EPILASIK -LASEK -Conductive Keratoplasty -Corneal Inlays and rings -Clear Lens extraction for myopia -Phakic IOL - Prelex Clear Lens Extraction with use of Multifocal IOL’s Combination of the two
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LASIK(Laser Assisted In Situ Keratomileusis) Procedure using laser to ablate the tissue from the corneal stroma to change the refractive power of the cornea
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Types of lasers used- Excimer-Excited dimer of two atoms -an inert gas(Argon) -Halide(Fluoride) which releases ultraviolet energy at193nm for corneal ablation
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Non-Excimer solid state lasers- 210nm Q switched diode pumped laser (laser off) 213 nm Q switched diode pumped laser(Pulsar)
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Advantage of Non-Excimer solid state lasers- No toxic excimer gases Wavelength closer to absorption peak of corneal collagen—less thermal and collateral damage Better pulse to pulse stability Not absorbed by air,water,tear fluid-so less sensitive to humidity or room temperature No purging with inert gases required.
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Patient selection Patients need to be fully informed about potential risks,benefits and realistic expectations Age should be above 18 years Refractive status should have been stable for at least 1 year. Current FDA approval- Myopia-upto -12D Hyperopia –upto +6D Astigmatism-upto 7D
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CCT such that minimum safe bed thickness left(250-270µ).Post op Corneal thickness should not be <410µ. Cornea not too flat or steep.<36D or>49D(Poor Optics).
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CONTRAINDICATIONS Systemic factors- Poorly controlled IDDM Pregnancy/lactation Autoimmune / connective tissue disorders(RA,SLE,PAN etc) Clinically significant Atopy,Immunosuppressed patients Keloid tendency(esp PPK) Slow wound healing-Marfans,Ehler-Danlos Systemic Infection-(HIV,TB) Drugs-Azathioprene,Steroids(Slow wound healing)
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CONTRAINDICATIONS Ocular Factors- Glaucoma,RP(Suction Pressure-ON damage,Blebs) Previous h/o RD or f/h of RD. One eyed individual Pre-existing dry eye,Keratoconus.pellucid marginal degeneration,Superficial corneal dystrophy,RCE,Uveitis,early Lenticular changes h/o Herpetic Keratitis(one year prior to surgery)
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PREOPERATIVE EVALUATION PRIOR TO LASIK Record UCVA and BCVA Snellens V/a Dry and wet manifest refraction(with 1% cyclopentolate) Pupillometry-Infrared Pupillometer -Aberrometer Large pupil-Increased HOA perceived so increased glare -Can change Optic Zone
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Slit Lamp Examination- Rule out blepharitis, miebomianitis, pingecula, Pterygium,corneal neovascularization Other contraindications for LASIK. IOP by applanation Dilated Fundus Examination to role out holes ,tears.
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Tear film asessment-Schirmers,TBUT and Lissamine staining Blink Rate-(Normal---3-7/min) Corneal Topography- Scanning slit/placido disc Stop RGP lenses 2 weeks prior and soft lenses I wk prior To rule out early Keratoconus and other ectasias For mean K values
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Pachymetry -For CCT (Ultrasound/Optical) Contrast Sensitivity testing for pre-operative baseline.
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BASIC STEPS AND MACHINE SPECIFICATIONS Topical anasthesia-Proparacaine 0.5%, Lignocaine 4%. Surgical Painting and draping(Lint Free). Lid speculum with aspiration. Corneal marking-Orientation of free cap
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Creation of flap- 1st Step-Creation of suction by suction pump to raise the IOP to 65 mm Hg which is necessary for the microkeratome to create a pass and resect the corneal flap. This is crosschecked with Barraquers tonometer.
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2nd step-Resection of corneal flap Microkeratome Femtosecond Laser (Intralase)
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Microkeratome- Uses Disposable blades Blade Plate can be set at 120µ,140µ,160µ and180µ. Nasal or superiorly hinge flaps can be created. Eg.Hansatome,ACS,Carriazo Barraquer, Moria.
Slide 19-

Femtosecond Laser for Flap- Creates photodisruption using femtosecond solid state laser with wavelength of 1053nm. Needs lower vacum. Very short pulse with spot size of 3µ-High precision cutting device. Any hinge can be made Can make flaps as thin as 100µ(Sub Bowmanns Keratomileusis)
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Flap has vertical edges –so reduced epithelial ingrowth. Microkeratome flap thicker in periphery and thinner in the centre.Not so with Intralase(Planar).
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3rd Step-Delivery of Laser- After flap is lifted, laser is applied to the stroma according to the ablation profile calculated by the machine. Laser beam is delivered by the following ways depending on the machine-
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Most machines employ a flying spot to deliver laser with the help of incorporated eye tracker.
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4th step-Reposition Of the Flap- After irrigating interface ,flap reposited Adhesion test-Striae test
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ABLATION PROFILES Wavefront Guided or customized ablation-to improve quality of vision by correcting higher order aberrations. -Wavefront analysis on entire eye done by –Hartmann Shack -Tracy
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ABLATION PROFILES Aspheric Ablation-Normal LASIK converts prolate cornea to oblate structure.(Central flattening,steep in periphery.) which induces higher order aberrations. To reduce this and preserve the prolate structure,’Q’ value is calculated and altered to give a more aspheric ablation.
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COMPLICATIONS OF LASIK Under/over correction and regression (over time). Post –op Keratectasia Presents 1-12 months Progressive regression Treatment-RGP,Corneal transplant. Prevention- Leave residual stromal bed -Do surface ablation -Don’t violatecorneal topography diagnosis of forme-fruste keratoconus
Slide 27-

COMPLICATIONS OF LASIK Night vision disturbances-Haloes/Glare Decenteration and central islands. Post Lasik Dry eye- Fluctuating vision,SPK Temporary neuropathic cornea Confocal microscopy-90% reduction in corneal nerve fibres-regeneration by 1 year. Rx-Preservative Free lubricants
Slide 28-

COMPLICATIONS OF LASIK Post op Glaucoma(Pseudo DLK)-Steroid induced. Vitreoretinal Complications- Increased risk of RD due to alteration of anterior vitreous by suction ring-Risk 0.08%. PVD(0.1% Risk) Macular Hemorrage(0.1% Risk)
Slide 29-

COMPLICATIONS OF LASIK Flap Complications- Button Hole-If K>50D,due to central corneal buckling. .
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Irregular thin flap-Inadequate suction/old blade Short Flap-Hinge encroaches on visual axis-Due to jamming of microkeratome with hair/FB SHORT FLAP
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Free Cap-Due to flat pre –op K(<38D).
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.Flap undulations- Macrostriae-Linear lines in clusters,seen on retroillumination. Causes-Incorrect position of flap -Movement of flap after LASIK Rx-Lift flap -Rehydrate and float it back -Check for flap adhesion MACROSTRIAE
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Microstriae-Flap in position but fine wrinkles seen superficially -Due to large myopic ablation -Rx- Observe.They resolve spontaneously MICROSTRIAE
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Bleeding during flap cutting due to corneal neovascularization in contact lens users
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Interface Inflammation(Sands Of sahara/DLK)-Non-Infective inflammation at the interface seen in 1st week after LASIK. Diffuse,confluent,white granular material at the interface 1-7 days after LASIK. Slight CCC No AC reaction Reduced Visual acuity
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Grade 1- Focal involvement - Normal V/A. Rx Intensive topical steroids.
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II – Diffuse involvement –Normal V/A. Rx-Add systemic steroids.
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III – Diffuse confluent granular deposits- Reduced V/A.No AC reaction. Rx-Same as above+Antibiotics IV - Diffuse confluent granular deposits +intense central striae. Marked Reduced V/A Rx-Interface irrigation + above
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Causes-Proposed Theory Bacterial cell wall endotoxin Cleaning solution toxicity Talc from gloves Miebomian secretions
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Infection-Potential complication as any surgical procedure
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Epithelial ingrowth-Presents 1-3 months after LASIK. Causes-Epithelial cells trapped under flap Risk factors-Peripheral epithelial defects -Poor flap adhesion -Buttonholed flaps -Repeat LASIK
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Classification- GRADE 1-Faint white line <2mm from flap edge GRADE 2-Opaque cells <2mm from flap edge with rolled flap edge GRADE 3-Grey to white fine opaque line extending >2mm from flap edge. GRADE 4-If ingrowth >2mm from edge with documented progression—Lift flap and remove the sheets of epithelium.Can use MMC.
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EPILASIK / LASEK Anterior stroma of cornea (ant. 1/3 rd) has stronger interlamellar connections than post. 2/3rd. So surface ablation preserves the structural integrity better than LASIK especially in the correction of moderate to high myopia.
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LASEK-Camellins Technique- 20% absolute alcohol used for 20-35s. To raise epithelial flap. Flap reposited after ablation
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EPILASIK- Epithelial keratome used to lift epithelial flap of about 60-80µ thick. Epithelial keratomes use - PMMA blades -Metal Epithelial Separator
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CONDUCTIVE KERATOPLASTY Uses mild heat from radiofreqoency waves to shrink collagen in the periphery of the cornea---This steepens the paracentral cornea. Used for hyperopia (1 – 2.25D) and presbyopia. C.K. spots are applied with a probe in rings with a dia. Of 6/7/8 mm. 8 spots are given in each diameter ring.
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5mm 6 7
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Drawbacks- Regression and retreatment in 100% cases after 6 months. Induced cylinder >1D reported in many cases. Usually done in one eye—Many have intolerance to monovision.
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CORNEAL INLAYS Increase the depth of focus by using pinhole optics. Inlays have 1.6mm centre with 3.6mm surround. Near vision improves by 1.5D with no loss of distant vision. Used in the non –dominant eye. These are hydrogel based.Placed in a tunnel 200-400 µ deep in centre of cornea.
Slide 50-

AcuSof Corneal inlay
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Phakic IOLs An intra-ocular lens is placed inside the eye in front of the patient’s natural lens. These are available in three types Anterior chamber angle fixated IOL – Nuvita (Bausch & Lomb), Kelman duet, I care (corneal), Vivarte (Ciba vision) Iris supported phakic IOL – Verisyse/ Artisan (AMO/Ophtec) Plate lens that fits between the iris & the crystalline lens – Starr implantable contact lens (ICL), PRL (Ciba).
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Indications Age above 18 years Stable refraction for one year Patients not suitable for LASIK/LASEK due to high powers or thin corneas AC depth 3.0 mm Endothelial count >2000cells/cumm No other ocular pathology
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Contraindications Myopia other than axial myopia Corneal dystrophy/ Endothelial cell count <2000cells/cumm Anterior chamber depth less than 3.0mm History of uveitis Presence of anterior/posterior synechiae Glaucoma or IOP higher than 20 mmHg Evidence of nuclear sclerosis or developing cataract Personal or family history of retinal detachment Diabetes mellitus
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Angle supported anterior chamber phakic IOLs – Rigid lenses
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Angle supported anterior chamber phakic IOLs – Foldable IOls
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Anterior Chamber Phakic IOL
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Kelman Duet phakic IOL Two piece phakic IOL. The PMMA haptic is first snaked through a 1.5mm incision. The silicone optic is then compressed & inserted. Once the optic unfolds in the anterior chamber the two tabs on either side of the optic are snapped into projections on the haptic. The main advantage of this lens is that the optic can be exchanged with a new one if the patient’s refraction changes.
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Iris fixated phakic IOL – Verisyse Phakic IOL Most commonly used phakic IOL One-piece design
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Verisyse Phakic IOL
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Pre-op assesment for phakic IOL Refraction – Objective & subjective acceptance at 12mm vertex distance Anterior chamber depth – from epiuthelium to endothelium Anterior & posterior segment examinations K-reading & Topography – Orbscan-II Intra-ocular pressure White to white measurement Specular microscopy
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Veriflex (artiflex) Foldable iris claw lens. It is a modification of Verisyse (Artisan) phakic IOl.
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Posterior chamber lenses These phakic IOLs are placed in the posterior chamber between the iris & the crystalline lens. These are Starr ICL Cibavision PRL
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STAAR ICL The STAAR Collamer ICL and the TORIC ICL are posterior chamber phakic intraocular lenses. Made of Collamer, STARR’s proprietary collagen copolymer (colagen/HEMA), the lens rests behind the iris in the ciliary sulcus.
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Procedure The lens is gently folded and injected into the anterior chamber through a 3.0 mm, temporal, clear corneal incision. The ICL is then carefully positioned by manipulating the footplates of the lens posterior to the iris plane and and into the sulcus. Pre-operative YAG iridotomy is essential.
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Complications ICL decentration Pupillary block Pigment dispersion Subcapsular cataract
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Advantages of phakic IOLs over laser corrective procedures A higher range of refractive errors can be corrected Reversible: Phakic IOL implantation is a potentially reversible procedure Safe: No structural changes are induced. Hence it is safe in any eye with high error & also thin corneas. Better quality of vision: Quality of vision (contrast sensitivity) is better than the laser refractive procedures in eyes with higher refractive errors and no induced higher order aberrations. There is also a considerable improvement in BVCA with these lenses because of the magnification effect. Highly skilled procedure: Prevents misuse of the procedure.
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Bioptics Bioptics is a combination of phakic IOL and LASIK. Bioptics is done for the correction of the residual spherocylindrical power when a spherical implant is used.
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THANK YOU